In the field of DNA computing, more and more efforts are made for constructing molecular machines made of DNA that work in vitro or in vivo. States of some of those machines are represented by their conformations, such as hairpin and bulge loops, and state transitions are realized by conformational changes, in which such loops are opened. The ultimate goal of this study is to implement not only independent molecular machines, but also networks of interacting machines, called chain reaction systems, where a conformational change of one machine triggers a conformational change of another machine in a cascaded manner. A chain reaction system would result in a much larger computational power than a single machine in the number of states and in the complexity of computation. As a simple example, we propose a generalpurpose molecular system consisting of logical gates and sensors. As a more complex example, we present a new idea of constructing a DNA automaton by a chain reaction system, ...